The balancing of product yield and marked demand of gasoline supplies, without the manufacture of large quantities of fractions having low commercial value, has for a long time required processes for the conversion of hydrocarbons of high molecular weight range and/or structure into smaller molecular weight range and/or structure. Basic processes for this are still the so called cracking processes in which heavy hydrocarbons and residues are broken down "cracked" into smaller, lower boiling molecules in the presence of high temperatures (380-540 C.), high pressures (100&gt;1000 psi) and often in the presence of added catalyst.
The energy to break the molecular bonds in refinery cracking processes is supplied by thermal motion of the molecules subjected to heating and excess pressure in addition to the effects of added catalyst(s).